Studies of nitrate balance in man and analyses of fecal and ileostomy samples indicate that nitrite and nitrate are formed de novo in the intestine, possibly by heterotrophic nitrification. These findings significantly alter our previous conceptions of man's exposure to nitrite and suggest that nitrite may play a role in the etiology of intestinal cancer via the formation of carcinogenic N-nitroso compounds. In the proposed research, we will conduct experiments to determine the effect of diet on formation of nitrite and N-nitroso compounds in man. These experiments will be performed on normal, healthy individuals, and on patients with ileostomies. We will explore the microbial formation of nitrite from ammonia and determine whether dietary variables including fat, protein, fiber, ascorbic acid, and alpha-tocopherol influence the formation of nitrite and its reactivity.